The present invention relates to a wastewater treatment device and a wastewater treatment method. The present invention relates to, as an example, a wastewater treatment device and a wastewater treatment method allowing advanced treatment of high concentration nitrogen wastewater containing hydrogen peroxide (e.g., high concentration ammonium-bearing wastewater containing hydrogen peroxide) discharged mainly from semiconductor plants as well as nitrogen contained in aminoethanol-bearing wastewater in compliance with the total volume control of nitrogen in conformity to partial amendments to Water Pollution Control Law implemented as of April 2004 while allowing energy saving and reduction in initial costs, running costs and maintenance costs.
Conventionally, it has been impossible in general to apply microbial treatment to high concentration nitrogen wastewater such as wastewater containing high concentration ammonium of approximately 3000 ppm since high organism toxicity.
Therefore, generally, the microbial treatment has been applied to nitrogen-bearing wastewater of low ammonium concentrations as low as several hundred ppm.
Accordingly, the wastewater containing high concentration ammonium of more than 3000 ppm has been concentrated to about 1/10 with use of an evaporator as a physical method. The resultant concentrated solutions have been placed as industrial wastes. In the method of concentrating the wastewater with use of the evaporator and discharging them as industrial wastes from plants, the concentrated solutions were deemed as industrial wastes. Therefore, this method has caused increase in industrial wastes from factories and caused problems such as air pollution due to use of fuel such as heavy oil because the concentrated solutions have generally been disposed as industrial waste by incineration. Moreover, the treatment method using the evaporator consumes a large quantity of energy and involves large plant equipment. This has caused a disadvantage of large initial costs, running costs and maintenance costs.
As another prior art, a biological treatment method has been disclosed in JP 2000-308900 A. The biological treatment in this prior art makes it possible to achieve stable treatment by preventing degradation of treatment efficiency caused by nitrite-nitrogen which is generated during treatment of wastewater containing high concentration ammonium-nitrogen. More specifically, the biological treatment method uses biological denitrification process involving autotrophic bacteria resistant to nitrite-nitrogen, in which the nitrite-nitrogen is removed from the wastewater by reducing the nitrite-nitrogen to nitrogen gas.
In the treatment method for ammonium-bearing wastewater, a nitrification tank, a denitrification tank, a UV oxidation tank, and treatments in the nitrification tank, a photocatalytic UV oxidation tank, the denitrification tank and the UV oxidation tank are disclosed.
A different biological treatment method is disclosed in JP 3467671 B2 as another prior art.
The biological treatment method is a nitrification-denitrification method in which organic wastewater in a raw water tank is sequentially fed to a denitrification tank and a nitrification tank with use of a feeding pump and circulated between both the tanks. Thereby, ammonia-state nitrogen contained in the organic wastewater is reduced to nitrogen gas by biological nitrification and denitrification actions. Further, sludge and treated water are separated from each other by using a suction pump and a filtration film unit sunk into wastewater in the nitrification tank.
A feature of the nitrification and denitrification method is that a pipe from the denitrification tank to the nitrification tank diverges in some midpoint, and an end of a diverging section is opened to the denitrification tank so that part of organic wastewater fed from the denitrification tank to the nitrification tank is ejected to the organic wastewater in the denitrification tank. That is to say, in this nitrification and denitrification method, wastewater is sequentially fed with use of the feeding pump to the denitrification tank and the nitrification tank while being circulated between both the tanks.
As yet another prior art, another biological treatment method is disclosed in JP 3095620-B.
In this biological treatment method, treatment is performed by a biological nitrogen rejection apparatus. The biological nitrogen rejection apparatus is provided with a denitrification tank for receiving inflow of raw water containing organic matters, a nitrification tank for receiving inflow of denitrification tank mixtures from the denitrification tank, a nitrified liquid circulation channel for circulating a nitrified liquid of the nitrification tank to the denitrification tank, and a nitrification tank air diffuser placed inside the nitrification tank.
More specifically, the biological nitrogen rejection apparatus has a denitrifying bacteria immobilization support charging zone placed in the denitrification tank in order to catch and remove suspended solids in the raw water flowing into the denitrification tank. Moreover, a raw water induction channel and a nitrified liquid circulation channel are linked to a lower position of the denitrifying bacteria immobilization support charging zone in the denitrification tank. Also, a sludge hopper section, which is for accumulating the suspended solids caught and removed in the denitrifying bacteria immobilization support charging zone, is provided on the bottom section of the denitrification tank, and a hopper air diffuser is provided in the sludge hopper section.
However, microbial treatment has not generally been applied to wastewater containing high concentration ammonium at about approximately 3000 ppm due to its high organism toxicity, as described above. More particularly, the high concentration ammonium wastewater which is too high in organism toxicity to undergo microbial treatment has been treated by the concentration method or the vaporization separation method. Accordingly, the concentration method has such problems as heavy consumption of energy and increase in industrial wastes caused by concentrated solutions, whereas the vaporization separation method has drawbacks such as inability to treat nitrous acid and nitric acid except ammonium in addition to heavy consumption of energy.
As yet another prior art, treatment method and device using nano-bubbles (bubble of diameter less than 1 μm) are disclosed in JP 2004-121962 A.
This prior art utilizes such characteristics of nano-bubbles as decrease in buoyancy, increase in surface area, increase in surface activity, generation of local high pressure fields, a surface active property and an antiseptic property attained by achievement of electrostatic polarization. More specifically, the prior art JP 2004-121962 A has disclosed that associating the above-stated characteristics with each other allows nano-bubbles to obtain a fouling component adsorption function, a substance surface high-speed cleaning function and an antiseptic function, and therefore, to effectively clean various substances with low environmental load and purify contaminated water
Still another prior art JP 2003-334548-A discloses a nano-bubble generation method.
This prior art has disclosed a process (1) for gasifying part of liquid by decomposition, a process (2) for applying ultrasonic waves to liquid, and a process (3) for gasifying part of liquid by decomposition with applying ultrasonic waves to liquid.
The two above-stated prior arts have disclosed the use of nano-bubbles for purification of contaminated water and removal of dirt on the surface of solids, but have not yet disclosed a technology for improving the efficiency of treatment and the quality of treated water when nitrogen containing wastewater is treated with microbes.